Altered Mosquitoes Quietly Tested in the U.S.

Bacteria-laden mosquitoes produce offspring that die quickly. China and the U.S. are releasing millions into the wild.

Genetically modified mosquitoes are all the rage these days. Tests are under way in Brazil to see if they can help fight off dengue fever and Zika virus, and a trial could soon start in Florida if opponents don’t stop it.

What fewer people know is that there’s a different kind of altered mosquito—one that doesn’t carry the “genetically modified” label—that’s already being tested out in the open in the U.S. and China.

These insects carry a type of bacteria, Wolbachia, that effectively renders them sterile. Release enough of them (usually millions, and usually males, because they don’t bite) and the wild population can dwindle. Think of it as birth control for bugs.

In the U.S., the insects are being developed by a Kentucky startup called Mosquito Mate, which has already released them in Los Angeles and has trials planned this summer in New York, Florida, and Kentucky.

A similar technology is also being used in China, where researchers now operate what may be the world’s largest mosquito factory. As of last year, four production units at the factory totaling 38,000 square feet were able to breed and release over a million mosquitoes a week, according to Zhiyong Xi of Michigan State University, who is involved in the project.

A tiger mosquito.

Both of these efforts target the Asian tiger mosquito, Aedes albopictus, an aggressive bug that’s been expanding its territory and which can transmit dengue fever. The mosquito is blamed for an outbreak of dengue in Hawaii that caused health officials to declare a state of emergency in February. It's also spreading dengue around Guangzhou, China.

Stephen Dobson, Mosquito Mate’s president and also a professor of entomology at the University of Kentucky, says that in the continental U.S. the bugs are being targeted mostly because they are “a nuisance.”

Albopictus are known to spread animal diseases, like dog heartworm and equine encephalitis, and there’s a risk they could spread other viruses, like Zika, whose recent emergence as a problem in the Americas has put a spotlight on new mosquito-control techniques.

On March 11, for instance, the U.S. Food and Drug Administration moved a step closer to allowing genetically modified mosquitoes developed by the company Oxitec to be tested in Florida. Just like the Wolbachia-carrying bugs, genetically modified mosquitoes also waste females’ time by producing offspring that die quickly.

By contrast, Mosquito Mate’s bugs have been released with hardly any public comment because they don’t have altered DNA. Instead, they’re regulated by the Environmental Protection Agency as “biopesticides,” says Dobson. He said the company has an experimental permit from the EPA to try the bugs, though they are not yet for sale.

“If you can do the same thing without saying GMO, it’s better,” says Guy Reeves, a molecular biologist at the Max Planck Institute for Evolutionary Biology, in Germany. “These guys got regulatory approval in six months, whereas the regulators sat on Oxitec’s application for three years.”

In the projects in China and the U.S., males get infected with a different version of the bacteria than wild females have. That creates an incompatibility that makes their copulation fruitless.

Any tactic using sterile insects needs to involve the release of a lot of males—typically, several times more than the number of mosquitoes in nature. It quickly adds up to millions of bugs. Dobson says Mosquito Mate can make a million a week right now, and could easily increase the number.

These Wolbachia mosquitoes shouldn’t be confused with another kind that’s been backed by the Gates Foundation and is being tested in Colombia and other countries. In that case, Aedes aegypti mosquitoes are getting infected with a different strain of the bacteria that doesn’t sterilize them, but instead makes it so that they can’t transmit dengue or Zika anymore.